Substrate processing method and material for electronic device

ABSTRACT

A method of processing a for an electronic device, comprising, at least: a nitridation step (a) of supplying nitrogen radicals on the surface of the electronic device substrate, to thereby form a nitride film on the surface thereof; and a hydrogenation step (b) of supplying hydrogen radicals to the surface of the electronic device substrate. By use of this method, it is possible to recover the degradation in the electric property of an insulating film due to a turnaround phenomenon which can occur at the time of nitriding an Si substrate, etc.

This application is a divisional of U.S. patent application Ser. No.10/485,410, filed Jan. 30, 2004, the entire disclosure of which isincorporated herein by reference and which is the U.S. national phase ofinternational PCT application PCT/JP02/07927, filed Aug. 2, 2002, andclaims priority to prior Japanese application 2001-235627, filed Aug. 2,2001.

TECHNICAL FIELD

The present invention relates to a method of processing a substrate forelectronic device by supplying nitrogen radicals, etc., to theelectronic device substrate, and a material for an electronic devicehaving a high-quality nitride film. The substrate-processing methodaccording to the present invention may particularly suitably be used,e.g., for forming a high-dielectric film on an electronic devicesubstrate.

BACKGROUND ART

In general, the present invention is widely applicable to the productionof materials for electronic device such as semiconductors orsemiconductor devices, and liquid crystal devices. For the convenienceof explanation, however, the background art relating to semiconductordevices as an example of the electronic devices, will be described here.

Substrates for semiconductors or electronic device materials such assilicon have been subjected to various kinds of treatments such asformation of an insulating film such as oxide film, film formation byCVD (chemical vapor deposition), etc., and etching.

It is not too much to say that the development in the performances ofsemiconductor devices in recent years is attributable to themicrofabrication technique concerning the semiconductor devices suchtransistor. At present, the microfabrication technique concerning thesemiconductor devices is being improved for the purpose of attainingfurther development in the performances of semiconductor devices.According to the recent requirement for forming microstructures andattaining further development in the performances in the field ofsemiconductor devices, the demand for an insulating film having a higherperformance (for example, in view of leakage current) has been increasedremarkably. This is because the leakage current of a certain degree cancause a severe problem in the recent devices which have attained finerstructure, and/or higher performances, even when the leakage current ofsuch a degree have actually caused substantially no problem in theconventional devices having a lower degree of integration. Particularly,in view of the development in the mobile or portable-type electronicdevices in a so-called “ubiquitous” society of recent construction(i.e., information-oriented society wherein people can use a networkservice, anytime and anywhere, by means of electronic devices), thereduction in the leakage current is an extremely important issue.

For example, with respect to the development of a next-generation MOStransistor, as the above-mentioned microfabrication technique isadvanced, the film-thinning of a gate insulator have approached a limitthereof, and a serious problem to be overcome is brought into view. Morespecifically, in view of processing technique, it is possible to thinthe film thickness of a silicon oxide (SiO₂) film which has been used asa gate insulator, to the utmost limit thereof (i.e., a levelcorresponding to one or two atom-layer). However, when film thickness isreduced to 2 nm or less, an exponential increase in the leakage currentis caused by the direct tunneling due to quantum effect, whereby theresultant power consumption is problematically increased.

At present, the IT (information technology) market is going to betransformed from the stationary-type electronic devices represented bydesktop type personal computers or home telephones (i.e., devicessupplied with electricity from a plug socket) into “ubiquitous networksociety” wherein people can access the Internet anywhere and anytime.Accordingly, it is considered that mobile terminals such as cellularphone or car navigation system will become predominant in the nearfuture. Such mobile terminals, per se is required to be ahigh-performance device. In addition, they should satisfy a prerequisitethat they are small-sized, light in weight, and have a function capableof being used for a long time, although these performances are notnecessarily required for the stationary-type devices. Accordingly, inthe field of a mobile terminal, it is an extremely important issue toaccomplish the reduction in power consumption and to accomplish theabove-mentioned high performances simultaneously.

Typically, for example, with respect to the development of theabove-mentioned next-generation MOS transistor, when themicrofabrication of a high-performance silicon LSI is investigated,there occurs a problem that the leakage current is increased and theresultant power consumption is also increased. Accordingly, in order toaccomplish a higher performance while reducing the power consumption, itis necessary that the performance of an MOS transistor is enhancedwithout increasing the gate leakage current therein.

With respect to the above-mentioned microfabrication, due to thedevelopment in the microfabrication technique, at present, it is nearlypossible to produce a super-microfabricated semiconductor device (suchas MOS transistor) having a gate length of 0.1 μm or less.

In such a super-microfabricated semiconductor device when the workingspeed of a semiconductor device is intended to be increased along withthe shortening of the gate length, it is necessary to reduce thethickness of gate insulator in accordance with the scaling law. Forexample, when a conventional thermal oxidation film is used as the gateinsulator, it is necessary to reduce the thickness of the gate insulatorto about 1.7 nm or less, for example. However, when the thickness of theconventional oxide film is reduced in this way, the gate leakage currentflowing through the oxide film is increased due to the above-mentionedtunnel effect.

For the above reason, heretofore, it has been investigated to use ahigh-dielectric film such as Ta₂O₅ or ZrO₂ as the gate insulator,instead of the conventional silicon oxide film. However, variousproperties of the high-dielectric film such as Ta₂O₅ or ZrO₂ are quitedifferent from those of the silicon oxide film which has heretofore beenused in the semiconductor technology. Accordingly, there remain a lot ofproblems to be solved, before such a high-dielectric film can actuallybe used as the gate insulator.

As a measure for solving such problems, it has been investigated to usea nitride film (and/or oxynitride film) as the gate insulator material.For example, the silicon nitride is the material which has been used inthe conventional semiconductor processes. In addition, the siliconnitride has a relative dielectric constant which is about twice that thesilicon oxide film, and is promising as the gate insulator for of thenext-generation high-speed semiconductor devices.

Heretofore, it has been usual that the silicon nitride film is formed onan interlayer dielectric (or interlayer insulating film) by using aplasma-CVD method. However, such a CVD nitride film generally provides alarge leakage current and also has a large absolute value of Vfb (flatband voltage), and therefore it is not suitable for the gate insulator.For this reason, it has never been attempted to use the nitride film asthe insulating film constituting a gate electrode.

On the other hand, there has recently been proposed a technique that anitrogen-containing gas such as nitrogen gas, nitrogen gas and hydrogengas, or NH₃ gas is introduced into a microwave-excited inert gas plasmasuch as argon or krypton, so as to generate an nitrogen radicals or NHradicals (however, the NH radicals are liable to provide danglingbonds), whereby the surface of a silicon oxide film is converted into anitride film. The thus formed nitride film may provide a leakage currentcharacteristic which is comparable to, or even superior to that of athermal oxidation film, and is promising as the gate insulator of thenext-generation high-speed semiconductor devices. In addition, there hasbeen proposed a technique that the surface of a substrate for electronicdevice is directly nitrided by such microwave plasma.

However, in the prior art, e.g., when the surface of a silicon oxidefilm formed on a substrate for semiconductor is modified or transformedby microwave-excited hydrogen nitride radicals NH*, there occurs adegradation in the resultant electric properties (for example, anincrease in the absolute value of Vfb, a change in threshold voltage),and a desired transistor characteristic has never been not accomplished.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a substrate processingmethod and a material for an electronic device, which can solve theabove-mentioned problem encountered in the prior art.

An object of the present invention is to provide a substrate processingmethod and a material for an electronic device, which can provide a gooddevice characteristic while avoiding the degradation of an electriccharacteristic, when a nitride film is formed on the surface of asubstrate for electronic device (comprising, e.g., a silicon surface oran oxide film surface) by a plasma nitriding process.

As a result of earnest study, the present inventors have found that itis extremely effective for solving the above problem to supply nitrogenradicals and hydrogen radicals in parallel at least partially, and/or tosupply nitrogen radicals and hydrogen radicals sequentially one afteranother, on to the surface of a substrate for an electronic device,instead of supplying NH radicals thereonto as in the prior art.

The substrate processing method according to the present invention isbased on the above discovery, and comprises: at least, a nitridationstep (a) of supplying nitrogen radicals on the surface of the electronicdevice substrate, to thereby form a nitride film on the surface thereof;and a hydrogenation step (b) of supplying hydrogen radicals to thesurface of the electronic device substrate.

The substrate processing method according to the present invention canprovide a good characteristic relating to electric property such as flatband voltage. According to the present inventors' investigations andknowledge, it is presumed that, when nitrogen radicals and hydrogenradicals are supplied in parallel at least partially, and/or nitrogenradicals and hydrogen radicals are supplied sequentially one afteranother, onto the surface of a substrate for an electronic device, thehydrogen radicals arrive at the interface or boundary between the rawmaterial (for example, silicon) and the nitride film which has beenformed thereon, to thereby terminate defects such as dangling bonds ofthe interface region of such a nitride film, etc. In addition, it ispresumed that the effective oxide thickness (EOT) of the resultantinsulating film to be formed can also be reduced by terminating thedefects such as dangling bonds of such an interface region, etc.

In the present invention, for example, as a result of the nitridation ofthe oxide film by a nitrogen radicals, a so-called turnaround phenomenonmay occur in some cases. This phenomenon is that, at first, as thesurface of the silicon oxide film is converted into a silicon nitridefilm, the electric film the thickness (i.e., effective oxide thickness)of the entire film is decreased, and the value of the leakage current isalso decreased as compared with that of a silicon oxide film having thesame effective oxide thickness; but after a certain point in time, theeffective oxide thickness of the entire film is reversely increased.According to the present inventors' investigations and knowledge, thisphenomenon may presumably be attributable to a phenomenon that thenitrogen arrives at the interface between the silicon oxide film and thesilicon so as to nitride the electronic device substrate, whereby thephysical film thickness of the entire insulating film is increased.

In the present invention, it has been observed a phenomenon such thateven when the Si surface is nitrided by such turnaround, the electricproperty such as flat band voltage is recovered by conducting hydrogenradical treatment. According to the present inventors' investigationsand knowledge, this may presumably be attributable to a phenomenon thatthe hydrogen radicals arrive at the interface between the silicon andthe nitride film, to thereby terminate defects such as dangling bonds ofthe interface region of such a nitride film, etc. In addition, it ispresumed that the effective oxide thickness of the resultant insulatingfilm to be formed can also be reduced by terminating the defects such asdangling bonds, etc., in the interface region between the silicon andthe nitride film.

On the other hand, in the prior art, when the surface of a silicon oxidefilm formed on a silicon substrate is modified or transformed bymicrowave-excited hydrogen nitride radicals NH*, there occurs aturnaround phenomenon as described above. In the prior art, when thesilicon substrate is nitrided, the flat band voltage of a MOS transistoris changed, and therefore the threshold voltage is changed, whereby adesired transistor characteristic is not provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is schematic sectional view showing an example of the structureor configuration of the substrate processing apparatus which is usablefor carrying out the method according to the present invention.

FIG. 2 is a schematic sectional view showing another example of thestructure or configuration of the substrate processing apparatus whichis usable for carrying out the method according to the presentinvention.

FIGS. 3A to 3D are schematic sectional views showing the substrateprocessing steps according to the first embodiment of the presentinvention.

FIGS. 4A to 4C are enlarged schematic sectional views partially showingthe substrate processing steps according to the first embodiment of thepresent invention.

FIG. 5 is a graph showing leakage current characteristic Jg and theeffective oxide thickness Teq of an insulating film which has beenprovided by the first embodiment of the present invention.

FIG. 6 shows a relationship between the flat band voltage and theeffective oxide thickness Teq which has been provided by the firstembodiment of the present invention.

FIG. 7A and FIG. 7B are graphs showing C-V characteristics which havebeen provided by the first embodiment of the present invention.

FIGS. 8A and 8B are views showing a process sequence of the firstembodiment of the present invention.

FIGS. 9A to 9C are views showing the substrate processing steps by thesecond example of the present invention.

In the above drawings, the reference numerals respectively have thefollowing meanings.

10: substrate processing apparatus

11: processing room

12: substrate-holding base

13: cover plate

14: shower plates

15: antenna

21: substrate for electronic device

22: silicon oxide films

22A, 23: silicon nitride film

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in detail withreference to the accompanying drawings as desired. In the followingdescription, “%” and “part(s)” representing a quantitative proportion orratio are those based on mass, unless otherwise specifically noted.

(Substrate Processing Method)

The substrate processing method according to the present inventioncomprises, at least, (a) a nitridation step of supplying nitrogenradicals onto the surface of an electronic device substrate, to therebyform a nitride film on the surface; and (b) a hydrogenation step ofsupplying hydrogen radicals onto the surface of the electronic devicesubstrate.

(Nitrogen Radical-Supplying Step and Hydrogen Radical-Supplying Step)

In the present invention, it is possible to use any order or sequence inthe time of the nitrogen radical-supplying step (a), and the hydrogenradical-supplying step (b), as long as it can achieve a predeterminedeffect (e.g., suitable flat band voltage as described hereinafter). Inother words, for example, the following embodiments are possibleconcerning these order of the step (a) and the step (b).

(1) The step (a) is conducted, and thereafter the step (b) is conducted.

(2) The step (a) and the step (b) are conducted in parallel.

(3) The step (a) and the step (b) are conducted so that they arepartially simultaneously (in other words, partially in parallel).

When the surface of an electronic device substrate to be processed bythe present invention comprises an oxide film, it is preferred to adoptthe above combination of (1). That is, it is preferred that the step (a)is conducted, and thereafter the step (b) is conducted. This is because,in general, an oxide film is comparatively less liable to be nitridedwhen the (nitrogen radicals+hydrogen radicals) are simultaneouslysupplied.

(Electronic Device Material)

The material for an electronic device according to the present inventionis an electronic device material which comprises a substrate for anelectronic device, and has a nitride film on at least a part of thesurface of the electronic device substrate; wherein the electronicdevice material provides a shift in the flat band voltage (Vfb) of 0.1 Vor less in NMOS, as compared with the flat band voltage of an oxidefilm, provided that the electronic device material is used as aninsulating layer constituting an MOS type device structure. The shift inthis Vfb in NMOS may preferably be 0.05 V or less, particularlypreferably 0.03 V or less. In the case of a PMOS, the electronic devicematerial may preferably be one providing a shift of 1 V or less. Theshift in the Vfb in PMOS may preferably be 0.5 V or less, particularlypreferably 0.3 V or less.

In the above-mentioned electronic device material, the phrase “thematerial has a nitride film on the surface thereof” means that thenitride film is in a position such that the film can be nitrided by theabove-mentioned combination of the nitrogen radical-supplying step (a)and the hydrogen radical-supplying step (b) (In other words, it is notnecessarily required that the nitride film is positioned on theoutermost surface of the electronic device material). In addition, inthe above-mentioned electronic device material, the phrase “at least onepart of the surface” means that the nitride film has a size and athickness which enable the nitride film to exhibit its function (forexample, function as the gate insulator of an MOS structure).

(Embodiment of Electronic Device Material)

The electronic device material having a nitride film on at least a partof the surface thereof may constitute a part of an arbitrary electronicdevice (such as semiconductor device, and liquid crystal device)specific examples of such an electronic device may include the followingexamples.

(1) Examples of a semiconductor device: e.g., semiconductor deviceshaving an MOS structure, more specifically, MOS type field-effecttransistor or capacitor/capacity, etc.

(2) Examples of liquid crystal device: e.g., liquid crystal deviceshaving a poly-silicon film on a glass plate, more specifically, TFT,etc.

(Flat Band Voltage)

The usage or application of the electronic device material according tothe present invention is not particularly limited. The high-qualitynitride film according to the present invention is particularly suitableas an insulating film of a semiconductor device (particularly, the gateinsulator of an MOS semiconductor structure).

When electronic device material according to the present invention isused, it is easy to produce an MOS semiconductor structure having theabove-mentioned preferred Vfb characteristic. In addition, when thecharacteristic of the nitride film which has been formed by the presentinvention is intended to be evaluated, instead of evaluating thecharacteristic of the nitride film per se, for example, it is alsopossible that a standard MOS semiconductor structure as described in apublication “Physics of VLSI Devices” written by Seigo Kishino &Mitsumasa Koyanagi, Matuzen, pp. 62-63 is formed, and the characteristicof the resultant MOS is evaluated. This is because, in such a standardMOS structure, the characteristic of the nitride film constituting theMOS structure has an important effect on the MOS characteristic.

One Embodiment of Substrate Processing Apparatus

FIG. 1 is a schematic sectional view showing an embodiment of theconfiguration or structure of a plasma substrate-processing apparatus 10which is usable in the substrate-processing method according to thepresent invention.

Referring to FIG. 1, the plasma substrate-processing apparatus 10 has aprocessing container 11 wherein a substrate-holding base 12 for holdingthereon a substrate w to be processed is disposed. The processingcontainer 11 is evacuated by exhaust ports 11A and 11B.

On the processing container 11, an opening is formed so that the openingcorresponds to the substrate w to be processed on the substrate-holdingbase 12, and this opening is covered with a cover plate 13 comprising alow-loss ceramic such as alumina. Further, below the cover plate 13,there is disposed a shower plate 14 comprising a low-loss ceramic suchas alumina, wherein a gas introduction passage and a number of nozzleopenings communicating with the gas introduction passage.

The above shower plate and cover plate 14 constitute a microwave window.On the outside of the above cover plate 14, there is disposed amicrowave antenna such as radial-line slot array antenna or electrichorn antenna.

In the operation of the device shown in FIG. 1 having the aboveconstitution, the processing space in the inside of the processingcontainer 11 is evacuated through the exhaust port 11A and 11B, so thatthe processing space is set to a predetermined processing pressure, anda desired process gas (such as oxygen gas, and nitrogen gas) isintroduced into the processing container 11 together with an inert gassuch as argon or krypton from the above shower plate 14.

Further, microwave having a frequency of several GHZ is introduced intothe processing container 11 from the antenna 15, so that high-densitymicrowave plasma is excited on the surface of the substrate W to beprocessed. In this way, the electron temperature of the plasma can belowered in the substrate-processing apparatus of FIG. 1 by exciting theplasma by microwave, to thereby avoid the damage or deterioration of thesubstrate w to be processed and the inner wall of the processingcontainer 11. In addition, the radicals which have generated by theaction of the plasma are caused to flow in the radial direction alongthe surface of the substrate W to be processed and rapidly discharged.Accordingly, it is easy to suppress the recombination of the radicals,and it is possible to efficiently conduct the uniform processing of thesubstrate, at a low temperature (for example, 550° C. or less).

Another Embodiment

FIG. 2 is a schematic sectional view showing another embodiment of theconfiguration of the plasma substrate-processing apparatus 10 which isusable in the substrate-processing method according to the presentinvention. The constitution of FIG. 2 is the same as the configurationof FIG. 1 except that a gas introduction port 14 a is used instead ofthe shower plate 14 for introducing a raw material gas in the embodimentof FIG. 1.

(Constitution of Respective Portions)

Next, there are described he electronic device material, or thesubstrate-processing method according to the present invention, or therespective portions constituting the substrate-processing apparatuswhich are suitably usable for the substrate-processing method.

(Electronic Device Substrate)

The electronic device material to be usable in the present invention isnot particularly limited, but may appropriately be selected from onekind or combination of at least two kinds of known electronic devicematerials. Examples of such an electronic device material may include:semiconductor materials, liquid crystal device materials, etc. Examplesof the semiconductor material may include: materials comprisingsingle-crystal silicon as a main component, materials comprising a metalas a main component, and materials comprising quartz as a maincomponent.

Examples of the liquid crystal device material may include: e.g., asubstrate having a poly-silicon film disposed on a glass plate.

(Process Gas for Supplying Nitrogen Radicals)

The process gas which is usable in the nitrogen radical supplying step(a) in the present invention is not particularly limited, as long as itcomprises a gas which is capable of supplying nitrogen radicals onto asubstrate to be processed. Such a gas to be used can appropriately beselected from one kind of known process gas, or combinations of two ormore kinds of known process gas which are usable for the production ofelectronic devices.

Specific examples of such a process gas may include the following gases.

(1) A mixture gas comprising an inert (or rare) gas and nitrogen gas(N₂).

(2) A mixture gas comprising an inert gas and ammonia (NH₃).

(Process Gas for Supplying Hydrogen Radicals)

The process gas which is usable in the hydrogen radical-supplying step(b) in the present invention is not particularly limited, as long as itcomprises a gas which is capable of supplying hydrogen radicals onto asubstrate to be processed. Such a gas to be used can appropriately beselected from one kind of known process gas, or combinations of two ormore kinds of known process gas which are usable for the production ofelectronic devices.

Specific examples of such a process gas may include the following gases.

(1) A mixture gas comprising an inert gas and hydrogen gas (H₂).

(2) A mixture gas comprising an inert gas and ammonia (NH₃).

(Inert Gas)

The inert gas to be usable in the present invention is not particularlylimited, but may appropriately be selected from one kind or combinationof at least two kinds of known inert gases usable for the production ofelectronic devices. The examples of such an inert gas may includekrypton (Kr), xenon (Xe), helium (He) or argon (Ar).

(Process Gas Condition)

In the nitride film formation according to the present invention, thefollowing conditions may suitably be used in view of the characteristicof the nitride film to be formed.

(Conditions for Nitrogen Radical-Supplying Step)

Inert gas (e.g., krypton, argon, He or Xe): 500-3000 sccm, morepreferably 1000-2000 sccm,

N₂: 10-500 sccm, more preferably 20-100 sccm,

Temperature: room temperature (25° C.) to 600° C, more preferably250-500° C., particularly preferably 250-400° C. Pressure: 3-400 Pa,more preferably 67-270 Pa, particularly preferably 67-130 Pa. Microwave(in a case where microwave plasma is used): 0.7-4.5 W/cm², morepreferably 1.4-3.6 W/cm², particularly preferably 1.4-2.8 W/cm²(Conditions for hydrogen radical-supplying step) Inert gas (e.g.,krypton, argon, He or Xe): 500-3000 sccm, more preferably 1000-2000sccm, N₂: 10-500 sccm, more preferably 20-100 sccm, Temperature: roomtemperature (25° C.) to 600° C, more preferably 250-500° C.,particularly preferably 250-400° C., Pressure: 3-400 Pa, more preferably67-270 Pa, particularly preferably 67-130 Pa.

Microwave (in a case where microwave plasma is used): 0.7-4.5 W/cm²,more preferably 1.4-3.6 W/cm², particularly preferably 1.4-2.8 W/cm².

(Radical-Generating Means)

In the present invention, the radical-generating means is notparticularly limited, as long as it may generate the above-mentionednitrogen radicals and/or hydrogen radicals. I low-temperatureprocessing, it is preferred to use plasma. Among this plasma, in view ofelectron temperature, plasma density, and uniformity, it is preferred touse the plasma based on microwave power supply, particularly the plasmabased on power supply using a plane (or flat-type) antenna member.

(Plane Antenna Member)

In the production process for electronic device material according tothe present invention, in view of the formation of plasma having a lowelectron temperature, a high density, and a high uniformity, it ispreferred to irradiate microwave via a plane antenna member having aplurality of slots. In the embodiment using such a plane antenna member,the nitride film is formed by using the plasma having excellentcharacteristic, and therefore the present invention can provide aprocess which accomplishes a light plasma damage, and a high reactivityat a low temperature. Further, in this embodiment, as compared with acase using conventional plasma, it is possible to obtain an advantagethat a nitride film having a profile wherein the nitrogen content isuniformly high in a plane may easily be provided by irradiatingmicrowave via a plane antenna member.

According to the present inventors investigations and knowledge, it ispresumed that the nitridation is conducted by using the high-densityplasma having a low electron temperature which has been generated byirradiating microwave via a plane antenna member having a plurality ofslots, and accordingly, the dangling bonds in the film are terminated inan ideal sate; and as a result, the insulation characteristic of thefilm per se can be improved, to thereby provide an electronic devicematerial (for example, semiconductor material) having an excellentcharacteristic.

(Preferred Plasma)

Preferred plasma characteristics of the plasma which may preferably beenused in the present invention are as follows.

Electron temperature: 0.5-2.0 eV

Density: 1E10 to 5E12 cm⁻³

Uniformity in plasma density: ±10% or less

(Use of Nitride Film)

In the present invention, a high-quality nitride film Can be formed.Accordingly, it is easy to form a semiconductor device structure havingan excellent characteristic by forming another layer (e.g., electrodelayer) on this nitride film.

(Suitable Characteristic of Nitride Film)

According to the present invention, a nitride film having the followingsuitable characteristic can easily be formed.

Gate leakage current: the gate leakage current may be reduced by afactor of 0.5 order (or digit) or more, as compared with that of aconventional thermal oxidation film,

Flat band voltage: the shift is 100 μV or less, as compared with that ofa conventional thermal oxidation film,

Uniformity in electric film thickness: 2% or less (σ/Ave).

(Preferred use of Semiconductor Structure)

The use of the method according to the present invention is notparticularly limited. The high-quality nitride film which can be formedby the present invention may particularly preferably be used as the gateinsulator of an MOS structure.

One Embodiment of Processing Method According to the Present InventionMethod

FIGS. 3A to 3C are schematic sectional views showing the substrateprocessing method according to the first embodiment of the presentinvention which uses the above-mentioned substrate-processing apparatus10 of FIG. 1.

Referring to FIG. 3A, an electronic device substrate 21 comprisingsilicon as a substrate W to be processed is introduced into theprocessing container 11 of the above substrate-processing apparatus 10.A mixture gas comprising krypton and oxygen is introduced into theprocessing container 11 from the above shower plate 14, and is activatedby microwave plasma to produce atomic oxygen O*. The surface ofelectronic device substrate 21 is processed by such atomic oxygen O*, tothereby form a silicon oxide film 22 having a thickness of 1.6 nm on thesurface of the electronic device substrate 21, as shown in FIG. 3B. Thethus formed silicon oxide film 22 has a leakage current characteristiccomparable to that of a thermal oxidation film which has been formed ata high temperature of 800° C. or more, although the silicon oxide film22 has been formed at a low temperature of about 400° C. Alternatively,the above silicon oxide film 22 may be a thermal oxidation film.

Next, in the step as shown in FIG. 3C, a mixture gas comprising argonand nitrogen is supplied into the processing container 11 in thesubstrate-processing apparatus 10 of FIG. 1, the substrate temperatureis set to 400° C., and plasma is excited by supplying microwavethereinto.

In the step of FIG. 3C, the internal pressure of the processingcontainer 11 is set to, e.g., 7 Pa, and argon gas at a flow rate of 1000sccm, and nitrogen gas is supplied, e.g., at a flow rate of 40 sccm. Asa result, the surface of the above silicon oxide film 22 is convertedinto a silicon nitride film 22A.

The step of FIG. 3C is continued for 20 seconds or more (e.g., for 40seconds), and as a result, the above the silicon nitride film 22A isgrown when the growth of the silicon nitride film 22A passes theturnaround point, the oxygen in the silicon oxide film 22 under thesilicon nitride film 22A begins to penetrate or invade into theelectronic device substrate 21.

FIGS. 4A to 4C schematically show the states or conditions of thesilicon oxide film 22 and the silicon nitride film 22A, before and afterthe turnaround point.

Referring to FIGS. 4A to 4C, FIG. 4A corresponds to the step of FIG. 3B, and shows a state wherein the silicon oxide film 22 has been formedon the electronic device substrate 21. FIG. 45 corresponds to an earlystage of the step of FIG. 3C, and shows a state wherein the surface ofthe silicon oxide film 22 is nitrided to thereby form a thin siliconnitride film 22A.

On the other hand, FIG. 4C corresponds to a state of the later stage ofthe step of FIG. 3C which has passed the turnaround point, and shows astate wherein the oxygen in the silicon oxide film 22 invades into theelectronic device substrate 21 along with the growth of the siliconnitride film 22A. This state is apparently similar to a state whereinthe silicon oxide film 22 has shifted into the electronic devicesubstrate 21. In FIGS. 4B and 3C, the reference A denotes the boundarysurface between the original silicon oxide film 22 and the electronicdevice substrate 21.

In the state of FIG. 4C, it is naturally considered that a flat andclear boundary surface (e.g., one as shown in FIG. 4B) is not formedbetween the silicon oxide film 22 and electronic device substrate 21,and a lot of silicon dangling bonds are formed. When such dangling bondsare present, the electric characteristic of the film is changed.Therefore, when a MOS transistor assuming such a state is formed, thethreshold voltage of the transistor is changed.

From the above point of view, in the present invention, hydrogen gas(e.g., 20 sccm) is added to the plasma from the above argon gas andnitrogen gas in the step of FIG. 3D, to thereby excite hydrogen radicalsH*.

The thus excited hydrogen radicals H* can freely pass through the entiresilicon nitride film 22A, unlike normal molecule H₂, and they easilyarrive at the silicon oxide film 22 under the silicon nitride film 22A,and further arrive at a portion in the vicinity of the interface betweenthe silicon oxide film 22 and the electronic device substrate, tothereby terminate the dangling bonds. As a result, when the hydrogenradical treatment as shown in FIG. 3D is conducted, it is possible torecover the degradation in the characteristic of the silicon oxide film22, which has been generated by the plasma nitriding treatment beyondthe turnaround point.

FIG. 5 shows a relationship between the leakage current characteristicJg and the effective oxide thickness Teq of the insulating film, whichhas been obtained by subjecting the silicon oxide film to the nitridingtreatment and the hydrogen radical treatment.

Referring to FIG. 5, it is found that the silicon oxide film 22 has afilm thickness of 1.7 nm at first, but the effective oxide thickness Teqthereof is decreased to about 1.5 nm by forming the silicon nitride film22A by use of the above nitriding treatment for 10 seconds. In addition,as shown by a straight line in this figure, the leakage current value Jgis decreased to about a half of the value thereof expected for siliconoxide having a thickness of 1.5 nm. Similarly, it is found that, whenthe above nitriding is conducted for 20 seconds, the effective oxidethickness Teq of the entire insulating film including the silicon oxidefilm 22 and the silicon nitride film 22A is further decreased, andfurther, the leakage current Jg is not increased. On the other hand, itis found that, when the above nitriding is continued for 40 seconds, theeffective oxide thickness Teq is further decreased so that the valueapproaches 1.4 nm. When the nitriding is further continued, the oxygenin the silicon oxide film 22 begins to invade into Si substrate 21, andthe total physical film thickness of the silicon oxide film 22 and thesilicon nitride film 22A begins to increase along with this phenomenon,as shown by an arrow in FIG. 5, the total effective oxide thickness ofthe entire films 22 and 22A begins to increase reversely.

On the other hand, referring to the view of FIG. 6 showing arelationship between the flat band voltage and the effective oxidethickness Teq, it is found that the flat band voltage of the MOSstructure which has been obtained by forming a poly-silicon gateelectrode on the above silicon nitride film 22A, is about −0.79 V and isnot substantially changed when the nitriding treatment time in FIG. 3Cis 20 seconds or less; but when the nitriding treatment time becomes 40seconds, the value is rapidly changed to −0.82 V. This is the effect ofthe turnaround which has been shown in FIG. 4C, and this means that theoxygen in the silicon oxide film 22 begin to invade into the electronicdevice substrate 21.

In FIG. 6, the symbols ▴ and ● denote the values of the flat bandvoltage which have been obtained when the hydrogen radical treatment ofFIG. 3D (H₂ repair) is conducted for 5 seconds and 10 seconds,respectively, on the sample which has been subjected to the abovenitriding treatment for 30 seconds beyond the turnaround point. Inaddition, FIG. 6 also shows the values of the flat band voltage whichhave been obtained when the hydrogen radical treatment is conducted for5 seconds and 10 seconds, respectively, on the sample which has beepsubjected to the above nitriding treatment for 15 seconds and 10seconds, which are not beyond the turnaround point.

Referring to FIG. 6, it is found that the flat band voltage is recoveredto −0.8 V which is near to the original value of −0.79 V, by subjectingthe sample (beyond the turnaround point) to the hydrogen radicaltreatment. In addition, it is also found that the flat band voltage isnot substantially changed, even by subjecting the sample (not beyond theturnaround point) to the hydrogen radical treatment.

Further, as shown in FIG. 5, it is found that when a sample which haspassed the turnaround point to a hydrogen radical treatment, theeffective oxide thickness is further decreased without causing a changein the leakage current. Herein, the points denoting the respectiveexperiments in FIG. 5 corresponding to those in FIG. 6 are denoted bythe same marks as those in FIG. 6.

FIGS. 7A and B show C-V characteristic which has been measured withrespect to the thus obtained insulating films.

Referring to FIG. 7B, the state of the flat band voltage recovery by thehydrogen radical treatment is explained. FIG. 7B shows a C-Vcharacteristic (capacity-gate voltage characteristic) of an MOScapacitor, and the gate voltage corresponding to 2.5 pF (flat bandcapacity: Cfb) in this figure corresponds to the flat band voltage. Withrespect to the oxide film (BaseOx 1.7 nm) in the a state of FIG. 3Bshown by a dotted line in this figure, a shift in the C-V characteristicis not observed, after the nitriding treatment for 20 seconds (1000/40 7Pa 20 s). However; after the nitriding treatment for 40 seconds (1000/407 Pa 40 s), the C-V characteristic is entirely shift to the minusdirection. In other words, the shift to the minus direction of the flatband voltage is observed. On the other hand, when a sample is subjectedto the nitriding treatment for 40 seconds, and thereafter subjected tothe hydrogen radical treatment for 5 seconds (1000/40 7 Pa 40 s→H₂Repair 5 s), the flat band shift which has been observed after thenitriding treatment for 40 seconds is recovered, the value after therecovery approaches the value of C-V characteristic of the oxide filmshown in FIG. 3B.

FIG. 8A shows a process sequence which has been used in the firstembodiment of the present invention.

Referring to FIG. 8A, in this embodiment, and plasma is first excited ina mixture gas comprising argon and N₂, and the resultant product issubjected to the nitriding treatment of FIG. 3C, and thereafter hydrogengas is added to the reaction system to thereby effect a hydrogen radicaltreatment.

In this embodiment, the addition of the hydrogen gas at the beginning isavoided, but hydrogen gas is added after the nitriding treatment issubstantially completed. As a result, the decrease in the plasma densitydue to the addition of hydrogen gas is avoided, it is possible toeffectively conduct the nitriding treatment.

In this embodiment, it is also possible to use a process sequence ofFIG. 8B, instead of using the process sequence of FIG. 8A.

In the process sequence of FIG. 8B, after the completion of thenitriding treatment, the supply of microwave is once interrupted, andthereafter plasma is newly formed in a mixture gas comprising argon gas,nitrogen gas, and hydrogen gas so as to conduct a desired hydrogenradical treatment.

Second Embodiment

FIGS. 9A to 9C show a substrate processing method according to a secondembodiment of the present invention. Herein, in these figures, the samereference numerals denote the portions which have already been explainedhereinabove, and the explanation thereof is omitted.

Referring to FIG. 9A, an Si substrate 21 is introduced into theprocessing container 11 of a substrate-processing apparatus 10 of FIG.1, and plasma is excited in a mixture gas comprising argon gas andnitrogen gas in the step of FIG. 9B, the surface of the above Sisubstrate 21 is processed by use of nitrogen radicals N* which have beenformed by the plasma excitation. As a result, a silicon nitride film isformed on the surface of the above Si substrate 21.

In this embodiment, in the step of FIG. 9C, hydrogen gas is furtherintroduced into the processing container 11 according to the sequence ofFIG. 8A, so that the surface of the substrate 21 is further processed bythe excited hydrogen radicals H*.

The thus formed hydrogen radicals H* may easily penetrate or invade intothe silicon nitride film 23, unlike hydrogen molecules, and they arriveat the interface between the Si substrate 21 and the silicon nitridefilm 23, to thereby effectively terminate the dangling bonds in Si.

In this embodiment, it is also possible to realize high-density plasmaat the time of the nitridation step of FIG. 9B by plasma-exciting themixture gas comprising argon gas and nitrogen gas. In this case, notonly the film quality of the thus formed nitride film may be improved,but also the throughput of nitriding treatment may be improved.

Hereinbelow, the present invention will be described in more detail withreference to Examples.

EXAMPLE 1

The nitride films which have been subjected to the above-mentionedrespective evaluations corresponding to FIGS. 5-7, were manufactured bya method comprising the following steps.

(1) Substrate

As the substrate, a 20 cm (8 inches) P-type silicon substrate was used,and the substrate had a specific resistance of 10 Ω cm, and a planeorientation of (100).

(2) Preliminary Washing Prior to Gate Oxidation

The natural oxide film and contaminating elements (metals, organicmatters, particles) were removed by using the RCA-washing by use of acombination of APM (a liquid mixture of ammonia, aqueous hydrogenperoxide, and pure water=1:2:10; 60° C.), HPM (a liquid mixture ofhydrochloric acid, aqueous hydrogen peroxide, and pure water=1:1:10; 60°C.) and DHF (a liquid mixture of hydrofluoric acid and pure water=1:100;23° C). The RCA-washing was conducted in the sequence of APM (10min.)→pure water rinse (10 min.)→DHF (3 min.)→pure water rinse (10min.)→HPM (10 min.)→pure water rinse (10 min.)→pure water final rinse (5min.), and thereafter IPA (isopropyl alcohol, 220° C.) drying wasconducted for 15 min., to thereby dry the water content on the wafer.

(Oxidation Process: Step 2A)

An oxide film (denoted by the reference numeral 22 in FIG. 4A) wasformed the silicon substrate which had been subjected to the abovetreatment (2), in the following manner.

Referring to FIG. 3A, an electronic device substrate 21 comprisingsilicon as a substrate w to be processed was introduced into theprocessing container 11 of the substrate-processing apparatus 10 shownin FIG. 1. A mixture gas comprising krypton and oxygen was introducedinto the processing container 11 from the above shower plate 14, and wasactivated by microwave plasma to produce atomic oxygen O*. The surfaceof electronic device substrate 21 is processed by such atomic oxygen O*,to thereby form a silicon oxide film 22 having a thickness of 1.7 nm onthe surface of the electronic device substrate 21, as shown in FIG. 3B.The thus formed silicon oxide film 22 had a leakage currentcharacteristic comparable to that of a thermal oxidation film which hadbeen formed at a high temperature of 800° C. or more, although thesilicon oxide film 22 had been formed at a low temperature of about 400°C.

<Processing Conditions>

1 Kr gas 2000 sccm

Oxygen gas 200 sccm

Temperature 400° C.

Pressure 260 Pa

Microwave 2.8 W/cm²

Processing time: For 1 min.

(Nitridation Step: Step of FIG. 3C)

Next, in the step of FIG. 3C, a nitridation treatment was conducted inthe substrate-processing apparatus 10 of FIG. 1 under the followingconditions.

<Processing Conditions>

Argon gas 1000 sccm

Nitrogen gas 40 sccm

Substrate temperature 400° C.

Pressure 7 Pa

Microwave 1.4 W/Cm²

Processing time 40 seconds

(Hydrogenation Step: Step 3D)

Next, in the step of FIG. 3D, a hydrogenation treatment was conducted inthe substrate-processing apparatus 10 of FIG. 1 under the followingconditions.

<Processing Conditions>

Argon gas 1000 sccm

Nitrogen gas 40 sccm

Hydrogen gas 20 sccm

Substrate temperature 400° C.

Pressure 7 Pa

Microwave 1.4 W/cm²

Processing time 5, 10 seconds

FIG. 5 shows a relationship between the leakage current characteristicJg and the effective oxide thickness Teq of the insulating film whichhad been obtained by subjecting the silicon oxide film to the nitridingtreatment and the hydrogen radical treatment. These relationshipsbetween the leakage current characteristic Jg and the effective oxidethickness Teq (FIG. 5), the flat band characteristic (FIG. 6), and C-Vcharacteristic (FIG. 7A and FIG. 7B) were obtained by fabricating adevice structure and measuring these properties in the following manner.

1: Substrate

As the substrate, a P-type silicon substrate was used, and the substratehad a specific resistance of 8-12 Ω cm, and a plane orientation of(100).

2: Preliminary Washing Prior to Gate Oxidation

The sacrificial oxide film and contaminating elements (metals organicmatters, particles) were removed by using the RCA-washing by use of acombination of APM (liquid mixture of ammonia, aqueous hydrogenperoxide, and pure water), HPM (liquid mixture of hydrochloric acid,aqueous hydrogen peroxide, and pure water) and DHF (liquid mixture ofhydrofluoric acid and pure water).

3: Plasma Oxidization Process

The silicon substrate which had been subjected to the above preliminarywashing prior to gate oxidation in the above step 2 was oxidized by thefollowing method. The silicon substrate which had been subjected to theabove treatment of step 2 was transferred into a reaction processingchamber in a vacuum state (back pressure: 1×10E-4 Pa or less), and thesubstrate was maintained at 400° C. Then, an inert gas (Kr) and oxygengas were flown onto the substrate at flow rates of 2000 sccm and 200sccm, respectively, and the pressure was maintained at 270 Pa (2 Torr).Such an atmosphere was irradiated with microwave of 2.8 W/cm² via aplane antenna member (SPA) having a plurality of slots so as to generateplasma including oxygen and the inert gas, and plasma oxidation wasconducted by using the thus generated plasma.

4: Plasma Nitridation Process

The oxide film which had been subjected to the treatment in the abovestep 4 was nitrided by the following method. Onto the silicon substratewhich had been heated to 400° C., an inert gas and nitrogen gas wereflown at flow rates of 1000 sccm and 40 sccm, respectively, and thepressure was maintained at 7 Pa (50 mTorr). Such an atmosphere wasirradiated with microwave of 1.4 W/cm² via a plane antenna member (SPA)having a plurality of slots so as to generate plasma including nitrogenand the inert gas, and an oxynitride film (SiON film) was formed on thesubstrate by using the thus generated plasma.

5: Thin-Film Formation by Hydrogen Plasma and Recovery of Vfb Shift

The oxynitride film which had been subjected to the treatment in theabove step 5 was after-treated by using hydrogen plasma in the followingmanner. Onto the silicon substrate which had been heated to 400° C., aninert gas and oxygen gas were flown at flow rates of 1000 sccm and 20sccm, respectively, and the pressure was maintained at 7 Pa (50 mTorr).Such an atmosphere was irradiated with microwave of 1.4 W/cm² via aplane antenna member (SPA) having a plurality of slots so as to generateplasma including hydrogen and the inert gas, and the oxynitride film wassubjected to hydrogen plasma treatment by using the thus generatedplasma.

6: Film Formation of Poly-Silicon for Rate Electrode

A poly-silicon film was formed by a CVD method as a gate electrode onthe silicon substrate on which the oxynitride film had been formed inthe above steps 1 to 6. The silicon substrate having the oxynitride filmformed thereon was heated to 630° C., and a silane gas was introducedonto the substrate at 250 sccm under a pressure of 33 Pa, and this statewas maintained for 30 min., to thereby form a poly-silicon film for anelectrode having a film thickness of 3000 A on the oxynitride film.

7: Doping of P (Phosphorus) to Poly-Silicon

The silicon substrate which had been obtained in the above step 6 washeated to 850° C., and POC13 gas, oxygen and nitrogen were introducedonto the substrate at normal pressure at 350 sccm, 200 sccm, and 20000sccm, respectively, and this state was maintained for 24 min., tothereby dope the inside of the poly-silicon with phosphorus.

8: Patterning Gate Etching

The silicon substrate which had been obtained in the above step 7 wassubjected to patterning by lithography, and the silicon substrate wasimmersed in a liquid chemical having a ratio of HF:HNO₃:H₂O=1:60:60 forthree minutes so as to dissolve a portion of the poly-silicon which hadnot been subjected to the patterning, to thereby fabricate an MOScapacitor.

<Method of Evaluating C-V Characteristic>

The C-V Characteristic was measured and analyzed in by the following. Atfirst, the characteristics of a capacitor having a gate electrode areaof 2500 μm² were evaluated at 100 KHz and 250 KHz, respectively, interms of C-V and D-V (D: loss factor). Then, there was analyzed the C-Vcharacteristic of the insulating film per se from which the parasiticcapacitance attributable to the measurement circuit, etc., was removedby using a two-frequency measuring method (SSDM 2000 Extended Abstracts,pp. 452-453, A Guideline for Accurate Two-Frequency capacitanceMeasurement for Ultra-Thin Gate Oxides, Akiko Nara et.al.). Morespecifically, the two-frequency measuring method was conducted in thefollowing manner. At first, by using respective frequencies of 100 KHzand 250 KHz, the gate voltage was scanned from +0.5 V to −2.1 V, tothereby evaluate the capacitance (C: capacity) and dissipation (D: lossfactor) at each voltage. HP 4284A apparatus was used as a C-V meter, anda Parallel mode was used as the measurement mode. The steps of thevoltage were 20 mV, and the measurement temperature was roomtemperature. From the thus obtained values of C and D, the capacity ofthe insulating film itself from which the parasitic capacitanceattributable to the measurement circuit, etc., was removed, wascalculated with respect to each of the above values of the gate voltageby using the formula corresponding to the two-frequency analysis thethus obtained values were used as the C-V characteristic of this MOSstructure. FIG. 7(a) and FIG. 7(b) show the C-V characteristics whichhad been analyzed by the above measuring method. FIG. 7(a) shows thevalues corresponding to the gate voltages from +0.5 V to −2.1 V, andFIG. 7(b) shows the values corresponding to the gate voltages from −0.6V to −1.0 V.

<Method of Analyzing Flat Band Characteristic>

Based on the fact that substrate concentration was 1E15/cm³, and theelectrode area was 2500 μm², the flat band capacity was calculated as2.5 pF. Accordingly, the gate voltage value at 2.5 pF was defined as theflat band voltage here. From FIG. 7(b), it was fond that the flat bandvoltage of the oxide film in this structure became about −0.8 V.

<Method of Evaluating Effective Oxide Thickness Teq>

From the thus obtained flat band value, the effective oxide thicknesswas obtained from the capacity value in the 0.6 V minus voltage side byusing the following method. When the flat band voltage is −0.8 V, thecapacity value in the 0.6 V minus voltage side becomes a capacity valueat the gate voltage of 0.8−0.6=−1.4 V. The relationship between thecapacity and the effective oxide thickness is as follows:(Capacity)=(vacuum dielectric constant)(dielectric constant of oxidefilm 3.9)×(capacitor area)÷(effective electric film thickness: Teff)  (Formula 1)(Effective oxide thickness: Teq)=1.0655×Teff−1.2923 (the unit of both ofTeq and Teff is nm)   (Formula 2)

Formula 1 is a formula capacity based on fundamentals of physics.

Formula 2 is an empirical formula which has been derived from therelationship between the ellipsometric film thickness and Teff. It ispossible to convert the value of Teff into the value of theellipsometric film thickness by using Formula 2.

Teff was obtained by substituting the capacity value at the gate voltageof −1.4 V in Formula 1, and the effective oxide thickness Teq wasobtained by substituting the thus obtained Teff value in Formula 2.

(Method of Measuring I-V Characteristic>

The I-V characteristic was determined by scanning the gate voltage from0 V to −2.4 V in the MOS capacitor having a gate electrode area of 2500μm², and evaluating the current value (leakage current value) flowing ateach of the voltages. The evaluation was conducted by using HP-4071Parametric Tester, and voltage steps of 20 mV.

The measurement was conducted at room temperature.

<Method of Evaluating Leakage Current Characteristic Jg>

In order to evaluate the leakage characteristic of this MOS capacitor,the leakage current value at the gate voltage which had shifted from theabove-obtained flat band value to 0.4 V minus direction, was determinedfrom the I-V characteristic. When the flat band voltage was −0.8 V, theleakage current at the gate voltage of −0.8−0.4=−1.2 V was used for thepurpose of evaluating the leakage characteristic.

INDUSTRIAL APPLICABILITY

As described hereinabove, according to the present invention, anelectronic device substrate is subjected to a nitriding treatment and ahydrogen radical treatment, whereby a defect such as dangling bonds in anitride film to be formed can be obviated.

Particularly, in the present invention, even when a nitride film isformed beyond the turnabout point, the problem encountered in the use ofsuch a nitride film can be solved by conducting a hydrogen radicaltreatment. As a result, for example, it is possible to restore a changein the flat band voltage and the threshold voltage of an MOS transistor.

Accordingly, the present invention can provide a nitride film which notonly has a very thin effective oxide thickness, but also provides and anelectric characteristic which is comparable to that of an oxide film,with respect to the flat band voltage and the threshold voltage.

1. A plasma processing apparatus, comprising: a processing chamber for plasma-processing a substrate for an electronic device; substrate-holding pedestal for holding the substrate in the processing chamber; plasma-generating unit for generating a plasma in the processing chamber; gas supply opening for supplying a process gas including nitrogen gas into the processing chamber; and evacuating means for evacuating the inside of the processing chamber; wherein the processing chamber performs the steps of: a) disposing the electronic device substrate on the substrate-holding pedestal in the processing chamber; b) generating nitrogen radicals in the processing chamber by using the plasma-generating unit, and supplying the nitrogen radicals to the surface of the electronic device substrate so as to nitride the surface of the electronic device substrate, to thereby form a nitride film on the electronic device substrate; and c) introducing a process gas comprising hydrogen gas into processing chamber via the gas supply opening, plasma-exciting the process gas by using the plasma-generating unit, so as to generate hydrogen radicals in the processing chamber, to thereby hydrogenate the nitride film with the hydrogen radicals in the chamber.
 2. A plasma processing apparatus according to claim 1, wherein the nitrogen radicals are formed by the plasma in a mixture gas of an inert gas and nitrogen gas.
 3. A plasma processing apparatus according to claim 2, wherein the plasma is excited by microwave.
 4. A plasma processing apparatus according to claim 2, wherein the inert gas is selected from the group consisting of Ar, Kr, He, and Xe.
 5. A plasma processing apparatus according to claim 3, wherein the plasma is generated by using a plane antenna.
 6. A plasma processing apparatus, comprising: a processing chamber for plasma-processing a substrate an electronic device; substrate-holding pedestal for holding the substrate in the processing chamber; plasma-generating unit for generating a plasma in the processing chamber; gas supply opening for supplying a process gas into the processing chamber; and evacuating means for evacuating the inside of the processing chamber; wherein the processing chamber performs the steps of: a) disposing the electronic device substrate in the processing chamber; b) introducing a process gas comprising nitrogen gas into processing chamber via the gas supply opening; c) plasma-exciting the nitrogen gas so as to generate nitrogen radicals in the processing chamber; d) nitriding the surface of the electronic device substrate with the nitrogen radicals, to thereby form a nitride film on the electronic device substrate; e) introducing a process gas comprising hydrogen gas into processing chamber via the gas supply opening; f) plasma-exciting the hydrogen gas so as to generate hydrogen radicals in the processing chamber; and g) hydrogenating the nitride film with the hydrogen radicals.
 7. A plasma processing apparatus according to claim 6, wherein the plasma is excited by microwave.
 8. A plasma processing apparatus according to claim 7, wherein the plasma is generated by using a plane antenna member.
 9. A plasma processing apparatus according to claim 6, wherein at least one of generating the nitrogen radicals and generating the hydrogen radicals is conducted at a pressure of 3-400 Pa.
 10. A plasma processing apparatus according to claim 9, wherein at least one of generating the nitrogen radicals and generating the hydrogen radicals is conducted at room temperature to 600° C.
 11. A plasma processing apparatus according to claim 6, wherein the nitrogen radicals are formed by the plasma in a mixture gas of an inert gas and nitrogen gas.
 12. A plasma processing apparatus, comprising: a processing chamber for plasma-processing a substrate an electronic device; substrate-holding pedestal for holding the substrate in the processing chamber; plasma-generating unit for generating a plasma in the processing chamber; gas supply opening for supplying a process gas into the processing chamber; and evacuating means for evacuating the inside of the processing chamber; wherein the processing chamber performs the steps of: a) disposing the electronic device substrate having an insulating film on the substrate-holding pedestal in the processing chamber; b) introducing a process gas comprising an inert gas and nitrogen gas into processing chamber via the gas supply opening, generating a plasma of the process gas by using the plasma-generating unit, so as to generate nitrogen radicals on the electronic device substrate; c) nitriding the surface of the electronic device substrate with the nitrogen radicals, to thereby form a nitride film on the electronic device substrate; d) introducing a process gas comprising hydrogen gas into processing chamber via the gas supply opening, and generating a plasma of the process gas by using the plasma-generating unit, so as to generate hydrogen radicals; and e) hydrogenating the nitride film with the hydrogen radicals.
 13. A plasma processing apparatus according to claim 12, wherein the plasma is generated by microwaves.
 14. A plasma processing apparatus according to claim 13, wherein the plasma is generated by using a plane antenna.
 15. A plasma processing apparatus according to claim 12, wherein the nitrogen-containing gas is selected from NH₃ and N₂, and the hydrogen-containing gas is hydrogen gas.
 16. A plasma processing apparatus according to claim 12, wherein the nitrogen radicals are formed by the plasma in a mixture gas of an inert gas and nitrogen gas.
 17. A plasma processing apparatus according to claim 1, wherein the nitrogen-containing gas is selected from NH₃ and N₂, and the hydrogen-containing gas is hydrogen gas.
 18. A plasma processing apparatus according to claim 6, wherein the nitrogen-containing gas is selected from NH₃ and N₂, and the hydrogen-containing gas is hydrogen gas.
 19. A plasma processing apparatus according to claim 11, wherein the inert gas is selected from the group consisting of Ar, Kr, He, and Xe.
 20. A plasma processing apparatus according to claim 16, wherein the inert gas is selected from the group consisting of Ar, Kr, He, and Xe. 